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Abstract
Purpose: The present work was carried out to reveal the involvement of histamine receptors at the neuro-melanophore junction of teleost, Oreochromis mossambicus.
Methods: The isolated scale melanophores were assayed using the mean melanophore size index and their responses were recorded in presence of various concentrations of histamine along with H1 and H2 receptor specific agonists and antagonist and potentiator compound 48/80.
Results: Melanophores showed high sensitivity to histamine and its specific agonists. Histamine caused a dose-dependent pigment aggregation, whereas 2-(2-Pyridyl) ethylamine (PEA), a specific H1R agonist also caused aggregation in a similar manner. Conversely, amthamine, a specific H2R agonist resulted in pigment dispersion. The effects were antagonized by mepyramine; specific H1R antagonist and ranitidine a specific H2R antagonist.
Conclusion: It is concluded that O. mossambicus melanophores have both H1 and H2 receptors which mediate melanophore aggregation and dispersion respectively. Compound 48/80 augmented the melanin-aggregating and dispersing effects of PEA and amthamine. It is suggested that the effect of histamine is directly mediated through H1 and H2 receptors, whereas H1Rs may be predominantly involved in the aggregatory responses.
Acknowledgment
We thank Principal and Secretary Saifia College of Science for providing necessary facilities for carrying out the study. Thanks are due to Dr. Rob Leurs, Center for Drug Research Leiden/Amsterdam for providing generous gifts of amthamine and ranitidine and Dr. Samreen Arshad, Sanofi-Aventis, Bridgewater, NJ, USA for a generous gift of mepyramine maleate.
Declaration of interest
The authors report no conflicts of interest.